#详细改进流程和操作，请关注B站博主：AI学术叫叫兽 
#详细改进流程和操作，请关注B站博主：AI学术叫叫兽 
#详细改进流程和操作，请关注B站博主：AI学术叫叫兽 
import torch
import torch.nn as nn
import math
from einops import rearrange
 #详细改进流程和操作，请关注B站博主：AI学术叫叫兽 
class AKConv(nn.Module):
    def __init__(self, inc, outc, num_param, stride=1, bias=None):
        super(AKConv, self).__init__()
        self.num_param = num_param
        self.stride = stride
        self.conv = nn.Sequential(nn.Conv2d(inc, outc, kernel_size=(num_param, 1), stride=(num_param, 1), bias=bias),nn.BatchNorm2d(outc),nn.SiLU())  
        self.p_conv = nn.Conv2d(inc, 2 * num_param, kernel_size=3, padding=1, stride=stride)
        nn.init.constant_(self.p_conv.weight, 0)
        self.p_conv.register_full_backward_hook(self._set_lr)
  #详细改进流程和操作，请关注B站博主：AI学术叫叫兽 
    @staticmethod
    def _set_lr(module, grad_input, grad_output):
        grad_input = (grad_input[i] * 0.1 for i in range(len(grad_input)))
        grad_output = (grad_output[i] * 0.1 for i in range(len(grad_output)))
 
    def forward(self, x):
        # N is num_param.
        offset = self.p_conv(x)
        dtype = offset.data.type()
        N = offset.size(1) // 2
        # (b, 2N, h, w)
        p = self._get_p(offset, dtype)
 
        # (b, h, w, 2N)
        # 得到左上角坐标q_lt，然后计算右下角坐标q_rb。
        p = p.contiguous().permute(0, 2, 3, 1)
        q_lt = p.detach().floor()
        q_rb = q_lt + 1

        # 限制q_lt和q_rb的坐标值在合法范围内（即特征图尺寸之内），避免越界访问。
        q_lt = torch.cat([torch.clamp(q_lt[..., :N], 0, x.size(2) - 1), torch.clamp(q_lt[..., N:], 0, x.size(3) - 1)],
                         dim=-1).long()
        q_rb = torch.cat([torch.clamp(q_rb[..., :N], 0, x.size(2) - 1), torch.clamp(q_rb[..., N:], 0, x.size(3) - 1)],
                         dim=-1).long()
        # 计算左下角坐标q_lb和右上角坐标q_rt，通过组合q_lt和q_rb的坐标值。
        q_lb = torch.cat([q_lt[..., :N], q_rb[..., N:]], dim=-1)
        q_rt = torch.cat([q_rb[..., :N], q_lt[..., N:]], dim=-1)
 
        # clip p-限制采样点坐标p，确保其也在合法范围内。
        p = torch.cat([torch.clamp(p[..., :N], 0, x.size(2) - 1), torch.clamp(p[..., N:], 0, x.size(3) - 1)], dim=-1)
 
        # bilinear kernel (b, h, w, N)
        # 构建双线性插值权重:这些权重基于采样点p与边界点坐标的相对距离。
        g_lt = (1 + (q_lt[..., :N].type_as(p) - p[..., :N])) * (1 + (q_lt[..., N:].type_as(p) - p[..., N:]))
        g_rb = (1 - (q_rb[..., :N].type_as(p) - p[..., :N])) * (1 - (q_rb[..., N:].type_as(p) - p[..., N:]))
        g_lb = (1 + (q_lb[..., :N].type_as(p) - p[..., :N])) * (1 - (q_lb[..., N:].type_as(p) - p[..., N:]))
        g_rt = (1 - (q_rt[..., :N].type_as(p) - p[..., :N])) * (1 + (q_rt[..., N:].type_as(p) - p[..., N:]))
 
        # 获取边界点像素值:
        x_q_lt = self._get_x_q(x, q_lt, N)
        x_q_rb = self._get_x_q(x, q_rb, N)
        x_q_lb = self._get_x_q(x, q_lb, N)
        x_q_rt = self._get_x_q(x, q_rt, N)
 
        # bilinear-利用双线性插值权重与边界点像素值进行加权求和，得到每个采样点的插值结果x_offset。
        x_offset = g_lt.unsqueeze(dim=1) * x_q_lt + \
                   g_rb.unsqueeze(dim=1) * x_q_rb + \
                   g_lb.unsqueeze(dim=1) * x_q_lb + \
                   g_rt.unsqueeze(dim=1) * x_q_rt
 
        x_offset = self._reshape_x_offset(x_offset, self.num_param)
        out = self.conv(x_offset)
 
        return out
#详细改进流程和操作，请关注B站博主：AI学术叫叫兽 
    def _get_p_n(self, N, dtype):
        base_int = round(math.sqrt(self.num_param))
        row_number = self.num_param // base_int
        mod_number = self.num_param % base_int
        p_n_x,p_n_y = torch.meshgrid(
            torch.arange(0, row_number),
            torch.arange(0,base_int))
        p_n_x = torch.flatten(p_n_x)
        p_n_y = torch.flatten(p_n_y)
        if mod_number >  0:
            mod_p_n_x,mod_p_n_y = torch.meshgrid(
                torch.arange(row_number,row_number+1),
                torch.arange(0,mod_number))
 
            mod_p_n_x = torch.flatten(mod_p_n_x)
            mod_p_n_y = torch.flatten(mod_p_n_y)
            p_n_x,p_n_y  = torch.cat((p_n_x,mod_p_n_x)),torch.cat((p_n_y,mod_p_n_y))
        p_n = torch.cat([p_n_x,p_n_y], 0)
        p_n = p_n.view(1, 2 * N, 1, 1).type(dtype)
        return p_n
 

    def _get_p_0(self, h, w, N, dtype):
        p_0_x, p_0_y = torch.meshgrid(
            torch.arange(0, h * self.stride, self.stride),
            torch.arange(0, w * self.stride, self.stride))
 
        p_0_x = torch.flatten(p_0_x).view(1, 1, h, w).repeat(1, N, 1, 1)
        p_0_y = torch.flatten(p_0_y).view(1, 1, h, w).repeat(1, N, 1, 1)
        p_0 = torch.cat([p_0_x, p_0_y], 1).type(dtype)
 
        return p_0
 
    def _get_p(self, offset, dtype):
        # n 是获取offset偏移量channels数量的一般
        N, h, w = offset.size(1) // 2, offset.size(2), offset.size(3)
 
        # (1, 2N, 1, 1)
        p_n = self._get_p_n(N, dtype)
        # (1, 2N, h, w)
        p_0 = self._get_p_0(h, w, N, dtype)
        p = p_0 + p_n + offset
        return p
 
    def _get_x_q(self, x, q, N):
        b, h, w, _ = q.size()
        padded_w = x.size(3)
        c = x.size(1)
        # (b, c, h*w)
        x = x.contiguous().view(b, c, -1)

        # (b, h, w, N)
        index = q[..., :N] * padded_w + q[..., N:]  # offset_x*w + offset_y
        # (b, c, h*w*N)
        index = index.contiguous().unsqueeze(dim=1).expand(-1, c, -1, -1, -1).contiguous().view(b, c, -1)
 
        x_offset = x.gather(dim=-1, index=index).contiguous().view(b, c, h, w, N)
 
        return x_offset
 
    @staticmethod
    def _reshape_x_offset(x_offset, num_param):
        b, c, h, w, n = x_offset.size()
        # using Conv3d
        # x_offset = x_offset.permute(0,1,4,2,3), then Conv3d(c,c_out, kernel_size =(num_param,1,1),stride=(num_param,1,1),bias= False)
        # using 1 × 1 Conv
        # x_offset = x_offset.permute(0,1,4,2,3), then, x_offset.view(b,c×num_param,h,w)  finally, Conv2d(c×num_param,c_out, kernel_size =1,stride=1,bias= False)
        # using the column conv as follow， then, Conv2d(inc, outc, kernel_size=(num_param, 1), stride=(num_param, 1), bias=bias)
        
        x_offset = rearrange(x_offset, 'b c h w n -> b c (h n) w')
        return x_offset
